U.S. patent number 7,063,994 [Application Number 10/617,413] was granted by the patent office on 2006-06-20 for organic semiconductor devices and methods of fabrication including forming two parts with polymerisable groups and bonding the parts.
This patent grant is currently assigned to Organic Vision Inc.. Invention is credited to Chunong Qiu, Cindy Xing Qiu, Steven Shuyong Xiao.
United States Patent |
7,063,994 |
Xiao , et al. |
June 20, 2006 |
Organic semiconductor devices and methods of fabrication including
forming two parts with polymerisable groups and bonding the
parts
Abstract
This invention discloses structures of organic materials-based
semiconductor devices and methods for the fabrication of such
devices. According to this invention, each of the devices has a
first part and a second part. The first part has at least a first
organic semiconductor material layer deposited on a first electrode
and the second part has at least a second organic semiconductor
material layer deposited on a second electrode. Said device is
formed by assembling the two individual parts together. Each part
maybe fabricated separately and consists of an electrode coated
with semiconductor organic materials required by the function of
the desired device. A schematic diagram in the FIG. 3 shows a first
part (11) consisting of a first substrate (13), a first electrode
(14) and at least one layer of organic materials (15); the second
part (12) of the device consisting of the second substrate (16), a
second electrode (17) with at least a layer of organic materials
(18). The organic device (10) is finally obtained by combining the
first part (11) with the second part (12) under controlled
environment. This is preferably done by aligning the first part
(11) onto the second part (12), and then by initiating a cross-link
between organic material (15) and organic material (18) via
heating, electron beam or light irradiation.
Inventors: |
Xiao; Steven Shuyong (Laval,
CA), Qiu; Chunong (Brossard, CA), Qiu;
Cindy Xing (Brossard, CA) |
Assignee: |
Organic Vision Inc. (Brossard,
CA)
|
Family
ID: |
33564957 |
Appl.
No.: |
10/617,413 |
Filed: |
July 11, 2003 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20050009227 A1 |
Jan 13, 2005 |
|
Current U.S.
Class: |
438/22; 438/99;
438/82; 438/29 |
Current CPC
Class: |
H01L
51/424 (20130101); B82Y 10/00 (20130101); H01L
51/0024 (20130101); H01L 51/4253 (20130101); H01L
2251/308 (20130101); H01L 51/0039 (20130101); H01L
51/0036 (20130101); Y02P 70/50 (20151101); Y02P
70/521 (20151101); H01L 51/0037 (20130101); H01L
51/0046 (20130101); H01L 51/0038 (20130101); Y02E
10/549 (20130101); H01L 51/56 (20130101); H01L
51/0043 (20130101) |
Current International
Class: |
H01L
21/00 (20060101); H01L 51/40 (20060101) |
Field of
Search: |
;438/22,29,82,99
;257/23,40,81 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
JM. Shaw, P.F. Seidler, IBM Journal of Research & Development,
45(1), 3(2001). cited by other .
C.W. Tang, and S.A. Vanslyke, Applied Physics Letter, 51,913(1987).
cited by other .
G. Czerremuszkin, M. Latreche and M.R. Wertheimer, WO03/005461,
Transparent support for Organic Ligh. cited by other .
A. Yasuda, W. Knoll, A. Meisel, T. Miteva, D. Neher, H.G. Nothfer
and U. Scherf, EP 1, 149 827 (2000. cited by other.
|
Primary Examiner: Brewster; William M.
Claims
What is claimed is:
1. A method to fabricate an organic electronic and opto-electronic
device comprising preparing a first part with at least a layer of a
first organic material containing a first polymerisable group,
preparing a second part with at least a layer of a second organic
material containing a second polymerisable group and subsequently
contacting the first polymerisable group with the second
polymerisable group, bonding said first part to said second part
under an environment with controlled parameters, wherein said
bonding of said first part and said second part is achieved by
cross-linking between said first polymerisable group and said
second polymerisable groups to form an active layer of an
opto-electronic device.
2. A method to fabricate an organic electronic and opto-electronic
device as defined in claim 1, wherein said first polymerisable
group is the same as said second polymerisable group.
3. A method to fabricate an organic electronic and opto-electronic
device as defined in claim 1, wherein said first polymerisable
group is different from said second polymerisable group.
4. A method to fabricate an organic electronic and opto-electronic
device as defined in claim 1, wherein said first polymerisable
group and said second polymerisable group are selected from a group
of alkyl, acrylate, epoxy, vinyl, vinyl ether, oxethane,
acrylnitrile, urethane, amino, hydroxyl, halide, isothiocynate,
isocynate, nitrile, or a mixture of at least two of the above.
5. A method to fabricate an organic electronic and opto-electronic
device as defined in claim 1, wherein said controlled parameters of
said environment include heating, electron beam radiation or light
lamination.
Description
FIELD OF THE INVENTION
This invention relates to structures of organic materials-based
semiconductor devices and the methods of fabrication the same.
BACKGROUND OF THE INVENTION
From light emitting diodes, solar cells, sensors, transistors to
many other semiconductor devices, organic materials with
controllable electronic and opto-electronic properties are emerging
as potential competitors to silicon, gallium aresenide and other
inorganic semiconductor materials as the backbones of the
semiconductor industry [J. M. Shaw, P. F. Seidler, IBM Journal of
Research & Development, 45(1), 3(2001)].
A simple organic semiconductor device may consist of one layer of
electro-opto active organic materials sandwiched between two
electrodes. However in practice, many layers of organic
semiconductor materials with different energy levels and
functionalities are often required in order to improve the device
performance. One typical example is an organic light-emitting
device (OLED) [C. W. Tang, and S. A. Vanslyke, Applied Physics
Letter, 51,913(1987)], as shown in FIG. 1. On a glass substrate
(1), a layer of ITO (2) is first deposited. This ITO layer (2) will
act as an anode. Then, a layer of hole-transport material (4) is
applied onto the anode (2). Following a layer of organic
semiconductor (5) is deposited onto the layer of hole-transport
materials (4), a low work function material is deposited in a
vacuum chamber by thermal evaporation or sputtering to form the
cathode layer (6). Finally, a protective top layer (7) is applied
in order to prevent oxygen or water molecules from reaching the low
work function cathode layer (6). This protective top layer (7) may
be a single layer of metal, glass, or multi-layers of metals and
dense polymer. A power supply may now be connected to allow a
current to flow into the organic semiconductor (5) through the ITO
layer (2). The flow of the current leads to recombination of charge
carriers in the organic semiconductor (5) to result in the emission
of light (8). In this typical OLED device (9), layer (1) is the
substrate, layer (2) is the anode, layer (4) is the hole-transport
media, layer (5) is the light emitting organic materials, layer (6)
is the cathode and layer (7) is the protective layer. In addition,
other layers, such as a layer of hole-injection materials and/or a
layer of electron-blocking materials may also be inserted between
anode layer (2) and hole-transport layer (4), and/or a layer of
electron-injection materials and/or a layer of electron-transport
materials may be inserted between cathode layer (6) and light
emitting organic semiconductor layer (5). These layers are chosen
to have properties such as hole or electron transport, hole or
electron blockage and light emission. Hence, it is clear that these
devices, including (9) are multi-layer structured.
Currently, multi-layer structured organic devices such as (9) are
conventionally constructed in a sequential manner. For instance in
the case of polymeric light emitting diode (9), as shown
schematically in FIG. 2. Firstly, a transparent electrode (2),
usually indium-doped tin oxide (ITO) is first vacuum sputtered on a
glass substrate (1). Secondly a hole-transport layer (4) such as
poly (3,4-ethylene-dioxythiophene) (PEDOT) is coated onto the layer
(2). Thirdly, a layer of light emitting polymer (5) such as
poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)
is coating onto the layer (4), fourthly a top electrode (6) such as
barium is thermally evaporated on layer (5) through a shadow mask.
Finally, a protective layer (7) such as aluminium is deposited. The
above fabrication steps yield a standard polymer light-emitting
device with a layer structure of Glass/ITO/PEDOT/MEH-PPV/Ba/Al. The
polymer (5) is commonly applied by spin coating or ink jet
printing, while the electrodes (2, 6) are usually constructed by
vacuum deposition or sputtering. Therefore, in this sequential
fabrication process, both wet processes and dry processes are often
required. One major drawback of this sequential fabrication is the
requirements to integrate the wet processes and the dry processes,
with total different working environments, into a single
fabrication chamber. Even though various layers on top of each
other can be processed by wet processing method, the choice of
solvent still remains a problem, because the solvent used for one
layer may attack the previously coated layer. Another drawback of
the sequential fabrication of the successive layers to form the
organic devices is the compatibility of the materials, specifically
the ones for anode and cathode. Moreover, organic semiconductor
devices, particularly these based on conjugated polymers, are
amenable to a roll-to-roll process to minimize production costs.
This sequential method is not flexible enough to meet the
requirements for a roll-to-roll process, especially for the
production of larger size flat devices. It is thus clear that a
simple manufacturing process is highly valuable for the fabrication
of these multi-layer organic semiconductor devices.
In the present invention, organic semiconductor devices containing
two parts, each part formed on a substrate with different
functional layers, are disclosed. By fabricating specific layers on
each substrate before combining the two parts to form the organic
semiconductor devices or circuits, the difficulties described above
on the integration of wet and dry processes can be overcome and the
fabrication cost can be reduced. The disclosed structure will allow
the fabrication of each of the two parts to be standardized in a
working environment or equipment which has been optimized
individually for each part. These two parts can be then assembled
in a specific way when needed. Hence, it is clear that the
disclosed structure formed by a combinational approach will dissect
a big project to various building blocks. This combinational
approach will reduce the equipment requirements for the
fabrication. More importantly, as compared to the sequential
approach, this combinational method will ultimately provide the
flexibility of varying combination possibilities of the final
device. For example, if five different first parts and five
different second parts are produced, up to twenty-five different
devices configurations can be constructed. From the above
description, it is evident that it is advantageous if an organic
device can be constructed by combining two different parts for mass
production.
OBJECT OF THE INVENTION
One objective of this invention is to provide an organic
materials-based semiconductor device with two parts, a first part
is formed on a first substrate with a first electrode and at least
one first organic layer and a second part is formed on a second
substrate with a second electrode and at least one second organic
layer. These two parts are combined to form the final device. This
combinatorial process provides versatility and flexibility in
constructing organic materials-based semiconductor device. Another
objective is to provide methods for fabrication of the organic
materials-based semiconductor devices with two parts, particularly,
methods of assembling the two parts into a single device.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic cross-sectional view of an organic
light-emitting device (9) with the bottom and top contact
electrodes deposited by vacuum methods.
FIG. 2 shows a schematic cross-sectional view of individual layers
of an organic device (9) using the sequential method.
FIG. 3 shows a schematic diagram of an organic device (10)
constructed by combining two parts (11, 12) according to this
invention; each of the two parts (11, 12) is fabricated in a
separate manner.
FIG. 4 is a schematic diagram showing electron-beam-induced
cross-linking of alkanes.
FIG. 5 is a schematic diagram showing molecular arrangement both
before and after cross-linking.
FIG. 6 shows chemical structures of typical materials used in
examples of this invention: (a) MEH-PPV used in examples 1, 5 and
7, (b) PFO-VE used in example 4, (c) P3BT-VE used in example 6 and
(d) PCBM used in example 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to one embodiment of this invention, as schematically
presented in FIG. 3, an organic semiconductor device (10) is
constructed by combining (or assembling) a first part (11) and a
second part (12) together. The first part (11) consists of a first
substrate (13), a first electrode (14) and at least one layer of
first organic semiconductor materials (15). The second part (12)
consists of a second substrate (16), a second electrode (17) and at
least one layer of second organic materials (18). The organic
semiconductor device (10) is obtained by combining the first part
(11) with the second part (12) under controlled environment. This
is done by bring the first part (11) towards the second part (12)
to initiate linking between the first organic material (15) and the
second organic material (18).
In FIG. 3, the first substrate (13) and the second substrate (16)
maybe selected from a group of rigid materials such as glass,
alumina, aluminium, brass, stainless steel sheet, etc., or from a
group of flexible materials such as polymeric sheets like
polyester, polycarbonate, polyamide, and textile fabrics, etc. The
selection of these substrates depends on the desired functionality
of the device. For example, in the case of OLED or other optical
devices, al least one of the two substrates (13, 16) shall be
transparent to permit optical signal passing through. If the first
substrate (13) is transparent, a bottom emission OLED may be
constructed, while if the second substrate (16) is transparent, a
top emission OLED may be fabricated. Furthermore, if both
substrates are transparent, a transparent OLED may be formed [M.
E.Thompson, S. R. Forrest, and P. Burrows, U.S. Pat. No. 5,986,401,
High Contrast Transparent Organic Light Emitting Device Display].
In addition, if flexible materials are selected for both
substrates, a flexible and foldable device may be constructed
[Takaaki, Ota, U.S. Pat. No. 6,490,402, Flexible Flat Colour
Display]. For a long-lived device, the air or moisture permeability
of these substrates shall be considered as well [G. Czerremuszkin,
M. Latreche and M. R. Wertheimer, WO03/005461, Transparent support
for Organic Light Emitting Device]. It is noted that in certain
cases, one or both substrates (13, 16) may be omitted depending on
the electrode layers (14, 17) used.
In FIG. 3, according to this invention, the first electrode layer
(14) and the second electrode layer (17) represent the cathode and
the anode of the device (10) respectively. Their energy levels and
electrical conductivity shall be first considered to facilitate
charges flowing through the device (10). For the case of OLED, low
work function materials such as metals (lithium, magnesium,
calcium, nickel, etc.), alloys and salts (LiF, CaF.sub.2,
MgF.sub.2, etc.) are preferable for layer (14) to act as the
cathode, whereas high work function materials such as metals
(platinum, gold, copper, silver, etc.), and metallic oxide (ZnO,
TiO.sub.2, ITO, etc.) are preferred for the second electrode layer
or anode (17). Optical transmission properties and compatibility of
the electrodes (14, 17) shall be considered according to the
selection of the first substrate (13) and the second substrate
(16). For instance, if the second substrate (16) is glass, a
transparent and electrically conductive material like ITO is more
preferable for the second electrode layer or the anode (17).
Commercially available transparent substrates with a transparent
electrode layer, for example ITO coated glass, can be selected for
the construction of the second part (12) of device (10). In such
cases, the glass will act as the substrate (16) and the ITO layer
will act as the anode (17). Similarly, a metallic sheet like
nickel, stainless steel may be preferable for the cathode (14),
where this metallic sheet will act as both the cathode (14) and the
substrate (13).
When a substrate with an electrode layer deposited is not
commercially available, it may be constructed via either a vacuum
or a non-vacuum processing. For the vacuum fabrication process, the
formation of the second anode (17) on the second substrate (16) and
the formation of the first electrode layer (14) onto the first
substrate (13) may be accomplished by chemical vapour deposition,
vacuum deposition, sputtering or spray pyrolysis. Using a
non-vacuum process, the fabrication of electrodes may be achieved
by electrolysis, spin coating, ink jet printing and other
non-vacuum techniques.
According to another embodiment of this invention, after the
formation of the first electrode (14) on the first substrate (13)
and the formation of the second electrode (17) on the second
substrate (16), at least a layer of the first organic materials
(15) is then applied onto the front surface of the first electrode
(14) and a layer of the second organic materials (18) is applied
onto the second electrode (17). The selection of the first and the
second organic materials (15, 18), either small molecules or
macromolecules, is dependent on the functions of device (10) to be
fabricated. More layers of organic materials (15', 15'' . . . not
shown in FIG. 3) may be deposited on the first layer of organic
material (15). Similarly, more layers of organic materials (18',
18'' . . . not shown in FIG. 3) may be deposited on the second
layer of organic material (18). The deposition methods of these
organic materials depend mainly on the nature of the organic
materials selected. A conventional solution processing technique
including spin coating, ink jet, screen-printing, thermal transfer
printing, etc., is preferred.
Clearly, it is important to select the correct organic materials
for the construction of these organic layers (15, 15' 15'' . . . or
18, 18' 18'' . . . ). The combination of these layers will
determine the functionalities of the final organic semiconductor
device fabricated. The first organic material layer (15) and the
second organic material layer (18) can be a single chemical
component or a mixture of different chemical components. These two
layers can have the same chemical composition or different chemical
compositions. The layer or layers of organic materials should have
the required electronic or electro-opto functions, and they should
also prevent the low work function electrode (14) from oxidization.
More preferably, the selected first organic materials (15) for the
first part (11) shall be able to chemically cross-link with the
second organic materials (18) for the second part (12). Hence, the
first organic material layer (15) of the first part (11) shall have
the first reactive groups (r1), and the second organic material
layer (18) of the second part (12) shall have the second reactive
groups (r2). These two reactive groups are selected so that they
can react to each other under controlled conditions. The first
reactive group (r1) and the second reactive group (r2) can be the
same or different as long as they can react to each other under
controlled conditions. The controlled conditions may include
temperature, pressure, and irradiation. Preferably, the reaction
between reactive groups (r1) and reactive group (r2) is
polymerization. In this case, reactive groups (r1) and reactive
group (r2) are called polymerisable groups. More preferably, this
polymerization can be initiated by heating, electron-beam or
UV-irradiation. FIG. 4 demonstrates the electron beam induced
cross-linking mechanism of two alkyl groups. Electroluminescent
polymers usually have flexible aliphatic side groups, which are
necessary to increase the solubility of the polymer in common
organic solvents. As shown in the first step of FIG. 4, when alkyl
groups are radiated by an electron beam or light beam, positively
charged molecules or excited molecules are formed which lead to the
formation of free radicals. In the second step of FIG. 4, these
radicals react with each other and lead the formation of
cross-links between these alkyl groups.
Cross-links form bridges among molecules and tie all the polymer
chains together to generate one giant super-molecule. FIG. 5 is a
schematic diagram that shows the formation of bridges between
polymeric material (15) and polymeric material (18), where the
polymeric material (15) represents the first organic material in
the first part (11) and the polymeric material (18) represents the
second organic material in the second part (12). In the figure,
arrows (20) symbolize the initiation of cross-links due to heating,
electron-beam or light radiation. While (25) represents bridges
formed among the molecules in the first organic material (15), (28)
represents bridges formed among the molecules in the second organic
material (18), and (30) represents bridges formed between the
molecules in the first organic material (15) and the molecules in
the second organic material (18). When molecules in the two organic
materials (15 and 18) become cross-linked, a lot of single
uncross-linked molecular chains wove together and form a
cross-linked network, which chemically bond the two layers (15 and
18) together.
In principle, any functional groups, which can react to each other,
can be selected as a polymerisable group. However, the
polymerisable or reactive groups (r1 or r2) are preferably selected
from alkyl, acrylate, epoxy, vinyl, vinyl ether, oxethane,
acrylnitrile, urethane, amino, hydroxyl, halide, isothiocynate,
isocynate, nitrile, and others. The selection of reactive group
(r1) or reactive group (r2) may be independent, but a
reaction-compatibility shall be considered. A preferable coupling
or polymerization system includes, but not limited to,
acrylate/acrylate, hydroxy/isothiocynate, vinyl ether/acrylate,
vinyl ether/vinyl ether, epoxy/epoxy, epoxy/vinyl ether,
epoxy/acrylate, epoxy/acrylate/vinyl ether, and many others.
Catalysts and/or photo initiators may be incorporated into the
formulation of the first organic materials (15) and the second
organic materials (18), respectively. The selection and use of
catalysts and/or photo initiators depend mainly on the nature of
the reactive groups (r1 and r2). But, a polymerization system with
photoinitiator-free and catalyst-free is much more preferable.
According to the above detailed description, the first part (11) of
device (10) is now constructed, which consists of the first
substrate (13), the first electrode (14) and at least a layer of
the first organic materials (15). Similarly, the second part (12)
is now constructed, which consists of the second substrate (16),
the second electrode (17) and at least a layer of the second
organic materials (18).
According yet another embodiment of this invention, a device (10)
is assembled by bringing the first part (11) and the second part
(12) together and promoting the cross-linking of organic materials
in said two parts (11 and 12) subsequently. It is thus clear that
the key features of the organic device (10) according to this
invention are the two parts (11,12), and assembling the two parts
(11, 12) to form an integral organic semiconductor device (10),
with the assistance of cross-linking or coupling between the
molecules. The coupling of the two parts (11, 12) is through
polymerization or cross-linking of the two polymerisable materials
(15, 18) previously coated on each of the two parts (11, 12),
providing a good interlayer adhesion in the two parts (11, 12) and
the evenness of the interfaces.
A combination of substrates (13 and 16), electrodes (14 and 17),
chemical composition of organic materials for each layer (15 and
18) would define the function of the organic semiconductor device
(10) fabricated. The organic semiconductor devices (10) which may
be fabricated according to this invention include but not limited
to organic thin film transistor (OTFT), organic photo-voltaic (OPV)
devices for solar cell application or detection, organic solid
state laser or organic solid state lighting (OSSL), organic thin
film memory (OTFM) for data storage, organic sensor (OS) for
bio-application and chemical detection, organic light emitting
diode (OLED) for flat panel applications and others.
For example in the case of a typical polymer light emitting device,
the first part (11) may be constructed by selecting silver as the
first substrate (13), magnesium as the first electrode (14), and a
polymerisable light emitting polymer (LEP) as the first layer of
organic material (15), forming a layer structure of Ag/Mg/LEP; the
second part (12) may be constructed by selecting glass as the
second substrate, ITO as the second electrode (17), and a layer of
polymerisable hole transport polymer (HTP) as the second organic
materials (18), forming a layer structure of HTP/ITO/Glass.
Aligning the first part (11) on top of the second part (12) and
inducing the cross-linking between the LEP and HTP will result in a
polymer light emitting device with a layer structure of
Glass/ITO/HTP/LEP/Mg/Ag, where HTP stands for hole transport
polymer such as polyaniline, polythiothene, polypyrole, etc, and
LEP stands for light emitting polymer such as polyfluorenes [A.
Yasuda, W. Knoll, A. Meisel, T. Miteva, D. Neher, H. G. Nothfer and
U. Scherf, EP 1, 149 827 (2000), End-capped polyfluorenes, film and
devices based thereon], polyphenylvinylenes [H. Spreitizer, W.
Kreuder, H. Becker, H. Schoo, and R. Demandt, U.S. Pat. No.
6,458,909 (2002), Aryl-substituted poly(p--arylenevinylenes),
process for their preparation and their use in electroluminescence
components], and others.
In the subsequent part of this invention, some examples on the
fabrication of OLEDs and TFT are given. It is clear that these
examples are presented for illustration purposes and not presented
to limit the scope of this invention.
EXAMPLES
Example 1
The Formation of the First Part (11) with a Light-Emitting
Polymer
A layer of nickel was first deposited onto a glass substrate by
conventional coating methods. Then onto the top surface of nickel,
a layer of semiconducting polymer MEH-PPV (structure shown in FIG.
6(a)) is spin-coated from a 1% wt./v of MEH-PPV in toluene at 2000
rpm. A low temperature heat treatment of the sample with the
semiconducting polymer is now carried out to vaporize the solvent
trapped within the polymer and to improve the molecule arrangement
within the film. The heat treatment may be carried out in an inert
atmosphere at a temperature in a range of 80.degree. C. to
120.degree. C., for a period ranging from 30 minutes to about 120
minutes, depending on the type of polymer used. This completes the
construction of the first part (11) of an organic semiconductor
device (10) that consists a nickel cathode covered by a
semiconductor polymer, i.e, Glass/Ni/MEH-PPV, where the glass is
the first substrate (13), nickel cathode is the first electrode
(14) and the MEH-PPV layer makes up the first organic material
layer (15), according to FIG. 3.
Example 2
The Construction of the Second Part (12) with a Hole Transport
Layer
In a chamber with flowing inert gas such as nitrogen, argon or a
mixture of them, a commercial ITO-coated glass is pre-cleaned by a
conventional technique. A layer of PEDOT is then spin-coated onto
the ITO-coated glass from a commercially available PEDOT solution.
This PEDOT-coated ITO glass will serve as the second part (12) of
the organic semiconductor device (10), where the glass is the
second substrate (16), ITO is the second electrode (17) and PEDOT
makes up the second organic material layer (18) according to FIG.
3.
Example 3
The Construction of an OLED
Example 1 provides the construction of the first part (11) of an
organic semiconductor device (10). It consists of the first glass
substrate (13), the first electrode (14) and the first organic
semiconductor material (15), with a structure of Glass/Ni/MEH-PPV.
Example 2 provides the second part (12) of an organic semiconductor
device (10) and it has a structure of Glass/ITO/PEDOT, where the
glass is the second substrate, ITO is the second electrode (17) and
the PEDOT is the second organic semiconductor material (18). An
OLED device (10) is then fabricated by stacking the first part (11)
with the second part (12), and this delivers a final device
structure of Glass/ITO/PEDOT/MEH-PPV/Ni/Glass. To have a better
interface contact between the first part (11) and the second part
(12), the two parts may be pressed while being heated. A
conventional encapsulation with epoxy resin is finally carried out
before the further characterization of this OLED.
Example 4
Heating Induced Cross-Linking of Conductive Polymers
In this example, the first part (11) is fabricated in a way similar
to the one described in example 1 except that a conjugated
co-polymer,
poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(9,9-di-{vinyloxybutyl}-fluorenyl-
-2,7'-diyl)] (PFO-VE, structure shown in FIG. 6(b)) is used to
replace the MEH-PPV used in example 1, forming the first part (11)
with a layer structure of Glass/Ni/PFO-VE.
The second part (12) in this example is fabricated in a manner
similar to the one described in example 2. After a layer of PEDOT
is spin-coated onto an ITO/glass electrode, a layer of PFO-PE is
applied onto the PEDOT layer and this forms the second part (12)
with a layer structure of Glass/ITO/PEDOT/PFO-VE.
After the first part (11) is properly placed onto the top of the
second part (12), the whole assembly is heated in a nitrogen-filled
chamber to a temperature of 100.degree. C. for 30 minutes. Thus an
OLED device (10) with a layer structure of
glass/ITO/PEDOT/PFO-VE/Ni/Glass is obtained.
Example 5
Electron-Beam Induced Cross-Linking of Conductive Polymers
This example is given to demonstrate an OLED device (10) fabricated
by electron beam induced cross-linking of electroluminescent
polymers. When flexible aliphatic side groups, for example
2-ethylhexyl in MEH-PPV (structure shown in FIG. 6(a)), are
subjected to high-energy radiation, such as electron beam, charged
and excited species are formed, which lead to the formation of free
radicals. These radicals can then react and lead to the formation
of cross-links as shown in FIG. 5.
In this example, the first part (11) with a layer structure of
Glass/Ni/MEH-PPV is fabricated in a way similar to that described
in example 1. The second part (12) is fabricated in a way similar
to example 2, except that after PEDOT is spin-coated onto the
ITO/glass electrode (17), a layer of MEH-PPV is applied onto the
PEDOT. This forms the second part (12) with a layer structure of
Glass/ITO/PEDOT/MEH-PPV.
After the first part (11) is properly placed onto the top of the
second part (12), the whole assembly is subjected to an
electron-beam radiation in a compact electron-beam processor under
dry nitrogen atmosphere. Thus an OLED device (10) with a layer
structure of Glass/ITO/PEDOT/MEH-PPV/Ni/Glass is obtained.
Example 6
A Plastic Solar Cell Fabricated from Cross-Linkable Conductive
Polymers
In this example, a bulk heterojunction of polymer/fullerence solar
cell based on poly (3-vinyloxybutyl-thiophene-2,5diyl (P3BT-VE,
structure shown in FIG. 6(c)), as an electron donor, and a soluble
fullerecne derivative [6,6]-phenyl-C61 butyric acid methyl ester
(PCBM, structure shown in FIG. 6(d)), as an electron acceptor, is
formed according to this invention. The first part (11) with a
layer structure of Au/Al/P3BT-VE:PCBM is prepared by deposition of
aluminium onto the front surface of a thin gold sheet. This is
followed by spin-coating a layer of P3BT-VE/PCBM onto the top of
the aluminium layer from a mixture of P3BT-VE/PCBM (at a 1:4 mass
ratio), dissolved in a chloroform-toluene solvent mixture (at 0.25
wt/%). A spinning speed of 4000 rpm is applied to yield a thin film
with a thickness of about 100 nm. The second part (12) with a layer
structure of ITO/PEDOT/P3BT-VE:PCBM is prepared by first
spin-coating a thin layer of PEDOT (Baytron P, Bayer AG, Germany)
on a patterned clean ITO-coated glass substrate. This is followed
by deposition of a thin P3BT-VE/PCBM layer onto the PEDOT layer. By
properly stacking the first part (11) onto the second part (12),
and then cross-linking the two parts (11, 12) via heating, a bulk
heterojunction of polymeric solar cell (10) with a layer structure
of ITO/PEDOT/P3BT:PCBM/Al is fabricated.
Example 7
An OLED Device Fabricated Via Conventional Method as a Reference
Sample for Comparison
For comparison, the conventional fabrication procedure for a
standard device configuration: ITO/PEDOT/MEH-PPV/Nickel/Glass is
given below.
A 130-nm-thick layer of PEDOT is first spin-coated (at 2000 rpm)
onto pre-cleaned ITO-glass substrates. After that, a light-emitting
polymer (MEH-PPV) with a thickness of about 80 nm is spin-coated at
room temperature under ambient conditions from a toluene/THF
solution. The solvent is then thoroughly removed by subsequently
baking the samples on a hot plate. The Ni cathode (50 nm thick) is
then deposited through a shadow mask at a chamber base pressure of
<10.sup.-6 torr. Finally, a glass substrate is stacked onto the
nickel layer with adhesive. This yields a standard OLED device with
a layer structure of ITO/PEDOT/MEH-PPV/Ni/Glass, which is identical
to the one prepared in example 3 according to this invention.
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